Electric motors are used in a variety of applications, including power tools. Electric motors may be brushed or brushless. In a typical brushed motor, the motor includes a motor armature coupled to a commutator assembly and a shaft, and a stator assembly that may include permanent magnets attached to the inner circumference of the stator. Two brushes may be provided in contact with the commutator assembly to drive the motor armature. The commutator is fixed for rotation with the motor shaft and provides an electrical connection between the rotating armature and the stationary brushes. Electrical leads selectively link the brushes to a power source. For a more detailed description of electric motors and power tools utilizing such motors, reference is made to U.S. Pat. No. 7,126,242 issued Oct. 24, 2006, and U.S. Pat. No. 7,893,586 issued Feb. 22, 2011, both of which are assigned to Black & Decker Inc, and both of which are incorporated herein by reference in their entireties.
FIG. 1 depicts a perspective view of a rotor assembly 100 including a motor armature 102 affixed to the motor shaft 104 for rotation with a commutator 106. The motor armature 102 may, for example, include a lamination stack that forms a series of peripheral slots 110. FIG. 2 depicts a cross-sectional view of the same rotor assembly 100 with a series of insulated conductive wires 108 wound in the armature slots 110 to form armature coils. A layer of insulating material (e.g., insulating paper) 112 is disposed within each lamination slot 110 to insulate the lamination slot 110 from the conducting wires 108. Ends of the wires are fused to segments of the commutator 106. Commutator 106 may, by way of example, include 24 independent segments.
An armature end insulator 114, commonly referred to as a stack insulation, end fiber or end spider, is provided at one or both ends of the armature lamination stack 102 in order to provide some separation between the lamination stack 102 and the conductive wires 108. The UL standards as relate to power tool industry safety features require a lamination stack end insulation of approximately 2 mm, although end insulation of 2.5 mm is common to account for material and process tolerances. Once the winding process is complete, a wedge (not shown) is inserted into the peripheral slots above the windings to shield the windings from dust and debris.
Winding the armature is typically performed in several stages, where a first round of coils is sequentially wound into the peripheral slots 110 followed by another, and this process is repeated until the slots 110 are filled to a desired level. A challenge in winding the armature is that it is difficult to position the wire coils within the peripheral slots in an efficient and compact manner to obtain the maximum amount of wire within each slot fill. Therefore, a mechanism to pack in the most amount of conductive wire into the slots is desirable.
According to an embodiment of the invention, an electric motor is provided including a stator and an armature received within the stator for rotational movement within the stator. In an embodiment, the armature includes an armature shaft on which a commutator is mounted, and a lamination stack also mounted on the armature shaft and having radially extending teeth that form slots therebetween. The slots are arranged circumferentially around a periphery of the lamination stack. The armature further includes end insulator arranged at an end of the lamination stack, the end insulator having a base portion fitted around the armature shaft and insulating teeth corresponding to the radially extending teeth of the lamination stack that form slots therebetween. In an embodiment, at least a portion of the insulating teeth has a greater thickness than at least a portion of the base portion. A set of coils are wound in the lamination stack slots and the end insulator slots. The shape of the end insulator according to this embodiment guides the coils to be wound more compactly in the lamination stack slots, as will be discussed in detail later.
According to an embodiment, the end insulator comprises an inner substantially flat surface mounted on the end of the lamination stack and an outer uneven surface formed by a flat surface of the base portion and at least one sloped surface of the insulating teeth. In an embodiment, each insulating tooth comprises a first extension surface extending from an outer surface of the base portion at a first angle. Each insulating tooth may further include a second extension surface extending from the first extension surface at a second angle. The second extension surface may be arranged at an angle of 0 to 10 degrees with respect to the outer surface of the base portion. In an embodiment, the base portion has a thickness of approximately 1-3 mm and the insulating teeth have various thickness levels between approximately 2 to 5 mm. In an embodiment, wherein each insulating tooth comprises two walls extending longitudinally and substantially in parallel from the inner surface of the end insulator to the outer surface thereof, said walls defining said plurality of slots of the end insulator. In an embodiment, each insulating tooth further includes a support rib corresponding to ribs at the ends of radially extending teeth of the lamination stack, the insulating teeth extending from the inner surface of the end insulator to the outer surface thereof.
According to an alternative embodiment of the invention, an electric motor is provided including a stator and an armature received within the stator for rotational movement within the stator. The armature includes an armature shaft on which a commutator is mounted, and a lamination stack also mounted on the armature shaft and having radially extending teeth that form slots therebetween. The slots are arranged circumferentially around a periphery of the lamination stack. In an embodiment, the armature further includes end insulator arranged at an end of the lamination stack, the end insulator having a base portion fitted around the armature shaft and insulating teeth corresponding to the radially extending teeth of the lamination stack that form slots therebetween. In an embodiment, at least one of the insulating teeth has a greater thickness than at least another of the insulating teeth. A set of coils are wound in the lamination stack slots and the end insulator slots.
In an embodiment, at least two of the insulating teeth that are arranged opposite one another have the same thickness as the base portion. In an embodiment, thicknesses of a subset of the insulating teeth gradually increase around the end insulator. In an embodiment, the base layer includes a main portion arranged along a first plane and two stepped surfaces arranged opposite one another along a second plane parallel to the first plane, and at least two of the teeth extend from the stepped surfaces. In an embodiment, the two stepped surfaces comprise a plurality of stepped sub-surfaces, and at least two of the plurality of teeth extend from each of the sub-surfaces. In an embodiment, the coils are wound in the slots adjacent the insulating teeth with the smallest thickness followed by slots adjacent to gradually thicker insulating teeth.
According to yet another embodiment of the invention, an electric motor is provided including a stator and an armature received within the stator for rotational movement within the stator. The armature includes an armature shaft on which a commutator is mounted, and a lamination stack also mounted on the armature shaft and having radially extending teeth that form slots therebetween. The slots are arranged circumferentially around a periphery of the lamination stack. The armature further includes end insulator arranged at an end of the lamination stack, the end insulator having a base portion fitted around the armature shaft and insulating teeth corresponding to the radially extending teeth of the lamination stack that form slots therebetween. In an embodiment, the end insulator has a uniform thickness of at least 5 mm. A set of coils are wound in the lamination stack slots and the end insulator slots.
The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.